POS machines are point-of-sale terminals with a function of non-cash settlement, which are used to complete transactions online by means of reading magnetic stripe information from a debit card via a card reader and entering personally identifiable information (password) by the cardholder, and they are applied to supermarkets, chain stores, hypermarkets, restaurants and so on. Since it concerns transactions online of debit card, it requires high safety performance and it must guarantee important data in the POS machine from being stolen.
To meet the data security standard, the present POS machine uses a method of surrounding the important data lines or sensitive elements via safe signal lines to prevent the illegal persons from detecting the important data lines and elements. If the CPU detects that the levels of the safe signal lines are changed, the CPU will erase all of the protected data.
The methods for protecting important data lines or sensitive elements via safe signal lines include wire-winding technology, contact protection technology and zebra technology. The wire-winding technology is generally achieved by disposing the safe signal lines on PCB according to a certain principle and manner and combining some PCB with wire wrapping, support and protecting frame and so on, so as to make the CPU and IC card chip be surrounded by the safe signal lines. If the electronic equipment is disassembled in anyway, the processor will erase all of the protected data. However, the wire-winding technology is complex and costly, and due to the need of wire wrapping surrounding the CPU and IC card chip, its development period is too long.
Contact protection technology is achieved by utilizing switching principle. The closing of the switch can be achieved by disposing the conducting resin on the contact and applying some pressure thereon. The zebra is similar to a switch, the conductive interlayer of which presents a certain conductivity after suffering pressure in a certain direction. The contact and zebra are used for preventing disassembly. If somebody attempts to detach the main case, mainboard and cover plate of the POS machine, the CPU will erase the protected data. However, this technology is costly.
Except the POS machine, there are ATM machine and all kinds of intelligent terminals provided to the public and working in unattended, the important date of which may be stolen.
Therefore, it is necessary to develop a method for protecting data information and protection circuit thereof with low costs and ease of maintenance.